What on earth do they think they are doing?!
I suggest that you copy and paste this....
I am 33 weeks pregnant.
I was given permission to wear my maternity clothes to work.
On 10th December XXX informed me that I had to wear my uniform again and that if I came to work in anything else I would be sent home unpaid.
So, on 11th December I wore one of my work dresses.
It was very tight and due to my obvious pregnacy.
XXX informed me that I was dressed inappropriately and that I must buy something else from work to wear.
I have no uniform allowance left so I would have to pay for this myself.
Even with a staff discount this will be a considerable expense at a time when I need to allocate my funds toward providing for my baby.
XXX then took me aside and said that she noticed I was 'standing about doing nothing'.
This is not true. I am not a lazy worker.
XXX said that 'they' don't feel I can do my job properly any more and have suggested I revise my maternity leave start date.
I was informed that another girl at work has been offered my position when I go on maternity leave.
I pointed out that I would be returning after maternity leave.
XXX said that she and the company have assumed I'm not coming back.
I am upset and concerned about what I consider to be this unfavourable treatment, due to my pregnancy, regarding my work clothes.
I am seriously concerned about my future job security now that I have been informed that it appears that the company doesn't intend to honour my right to return to work after my maternity leave.
I would appreciate a written response to my concerns at your earliest convenience.
Yours etc.
Print 3 copies. Keep one for yourself. Hand two copies to HR and get whoever you hand them to to sign and date one of them and immediately return it to you, so that you can prove receipt.